A variety of vehicles are known which drive an engine (internal-combustion engine) without idling for stopping operation of the engine, at predetermined timing, while a vehicle is stopped in its travel, for saving energy saving and abatement of environmental pollution.
In a vehicle, on heating, warm air produced by heat exchanging between cooling water of the engine is provided or inducted inside of a vehicle compartment to provide a comfortable environment therein. However, when the engine stops, as a pump circulating cooling water residing in a heat exchanger stops its operation, it does not replenish heat storage volume used for heating of warm air. Accordingly, it falls into a situation where temperature of the heat exchanger drops in accordance with time elapsed from the engine stopping, such that it will be unable to blow out sufficiently heated warm air inside of the vehicle compartment.
In the vehicle of this kind, as heating becomes poor where the temperature of warm air drops, with the engine stop on no idling, and when ambient air temperature is lower than a given temperature, it has been heretofore proposed to prohibit execution of the no idling or engine stop (see Patent Document 1). Further, because on no idling, it is difficult to sufficiently heat the cool ambient air, it has been proposed to switch from ambient air induction where ambient air is inducted to heat a vehicle compartment to interior air circulation where air in the vehicle compartment is circulated (see Patent Document 2). Furthermore, when execution of the idle stop is not prevented, it has been proposed to switch to interior air circulation where little air volume is supplied as cold ambient air (see Patent Document 3).